It sure can be hard getting perfectly straight horizon lines, especially when it comes to the Sea or coastlines.

When it comes to the Sea, remember it isn't a straight line when viewed with a sufficiently wide field, and your lens may also not be geometrically perfect.

Coastlines around the Sea or lakes can also be very tricky as there may be a slight natural diagonal from your viewpoint, but it ends up looking squint on a photo. Sometimes even when the spirit level in your tripod tells you it's technically right, the photo looks better if you tilt the camera so what looks like a horizon line really is straight across the image.

This is why I love grids, whether electronic or optical, so much!

I guess if the optical viewfinder weren't 100% square you could also have a problem, where even when it looks correct, the image will be a little squint. I'm not sure if any cameras suffer from this more than others, but it's another advantage for having a Live View feed direct from the sensor...

I reported before that I noted some of my pictures were turning right. The example I provided wasn't maybe the more explicit , but more pictures, especially for architecture, suffered from the same problem .

Personally, IMHO, I rather prefer simplicity and quality rather than new features, that may bring their own drawbacks as well as uncorrect usage by the photograph (like the shake reduction switched on while on a tripod )... And how to check a 1° spin on a 2" screen?

Back to my K10D, I went to Pentax France this afternoon, and let my K10D to be repaired. After a quick review and thanks to the pictures above, the after-sales technician said the focusing screen on the viewfinder may have moved a little. Fixing it would take two weeks. That means two weeks without taking picture

I'm pleased your viewfinder and sensor are now aligned, but that is annoying that they're not aligned with the body!

Sadly I suspect many DSLRs suffer from this sort of error and most people just put it down to human error.

Maybe there is some warp in your wooden sheet? I would prefer to see a test where the camera is mounted on a tripod with a spirit level, so that you know it is absolutely level. Then again this is also prone to error as the base plate and tripod mount may not be perfectly square. You could alternatively try a hotshoe mounted spirit level, but again the hotshoe may not be square either. It's a tricky one to test.

Actually, I rather prefer to get what I see on the viewfinder that having a picture aligned with the body, since the camera is mostly on my hands and a dSLR is based on the viewfinder. That's why I'm happy with the fix.

My main disappointment is originated by the fact my K10D comes from the very Pentax repair shop with a new flaw and no explanations! I would try to get some answers from Pentax. Maybe other K10D users are experiencing the same troubles

But, most important, I could now take pictures consistent with what my eyes see

I'm glad you've got the viewfinder correctly aligned with the sensor now as that's a pretty fundamental requirement. If I've got my sums right, assuming the sensor assembly is attached to the body with mounting points 20mm apart a 1° misalignment could be the result of a tolerance of 175 microns at each mounting point. I'm not qualified to know whether that is good or bad with today's assembly methods but I suspect that a lot of cameras might have this problem as the chances of ever noticing it in real life situations, as opposed to the test bench, are slim.

I fully agree with you: having the viewfinder correctly aligned with the sensor is the msot important.

However, what I don't understand is why the Pentax maintenance department moved the sensor (instead of the viewfinder) to correct the misalignment of the viewfinder with both the sensor and the body (the sensor and the body were aligned).